This invention relates to solid state ignition systems for internal combustion engines particularly as applied to larger outboard motors employing two cycle engines.
High horsepower outboard motors generally include an engine with four or more cylinders. The engine is coupled to the propeller unit by a gear shift means having neutral, forward, and reverse gear settings. Shifting generally is done by the operator with the engine at idle speed. Stalling of the engine may result from sudden application of the propeller load, such as by rapid shifting between a brisk forward boat speed to reverse idle, or if the water level should rise above and block the idle relief exhaust ports and create excessive crankcase back pressure conditions. Various other conditions may also exist which result in improper engine operation at idle or low speed. Improper engine idle operation may for example be caused by dirt in the carburetor, water in the fuel supply, as well as an improper air-fuel mixture. Various electrical system problems such as fouled spark plugs, electrical supply failures to one or more of the spark plugs and the like may also cause poor engine operation under idle speed conditions. These and similar conditions which interfere with proper idle speed operation further increase the probability of stalling the engine. An electronic idle speed control which has been satisfactorily used since early 1977 in two cylinder, two cycle outboard motors of relatively low horsepower, such as a four horsepower outboard motor unit, is disclosed in the copending application of Arthur O. Fitzner et al entitled IGNITION SYSTEM WITH IDLE SPEED GOVERNOR APPARATUS which was filed on Jan. 4, 1977 with Ser. No. 756,649, now U.S. Pat. No. 4,111,174. The system disclosed therein has provided improved operation under certain conditions but has not avoided the various faults noted above in the larger engines. The system was also found to be subject to various manufacturing and assembly tolerances.